The invention relates to a thin film magnetic head, a head gimbals assembly, a head arm assembly, and a magnetic disk unit.
A magnetic disk unit has been used for writing and reading magnetic information (hereinafter, simply referred to as information). The magnetic disk unit may include, for example, in a housing thereof, a magnetic disk in which information is stored, and a thin film magnetic head that writes information into the magnetic disk and reads information stored in the magnetic disk. The magnetic disk is supported by a rotary shaft of a spindle motor, which is fixed to the housing, and rotates around the rotary shaft. In contrast, the thin film magnetic head is formed on a side surface of a magnetic head slider provided on one end of a suspension, and includes a magnetic write element and a magnetic read element that have an air bearing surface (ABS) facing the magnetic disk. In particular, as the magnetic read element, a magnetoresistive (MR) element exhibiting MR effect is generally used. The other end of the suspension is attached to an end tip of an arm that is supported and allowed to pivot by a fixed shaft that is installed upright inside the housing.
Incidentally, in recent years, along with a progress in higher recording density (higher capacity) of the magnetic disk, reduction in recording track width is progressing. Such reduction in recording track width results in reduction in the size of the thin film magnetic head. Thus, signal recording performance of the magnetic write element on the magnetic disk is weakened and intensity of signal magnetic field from the magnetic disk is weakened as well. To compensate deterioration in these functions, for example, it may be necessary to generate a stronger write magnetic field or reduce size of a magnetic spacing (bring the ABS of the thin film magnetic head closer to a surface of the magnetic disk).
Accordingly, for example, to generate a strong write magnetic field, it is conceivable to cause a larger write current to flow during information writing operation. In a case of causing a large current to flow, however, the thin film magnetic head itself generates heat, which may cause expansion of the thin film magnetic head toward the magnetic disk that is so-called thermal protrusion. When thermal protrusion occurs in such a way, reliability of the magnetic recording device may be impaired.
A large number of technologies to suppress occurrence of thermal protrusion have been reported. For example, U.S. Pat. Nos. 6,842,308 and 6,989,963 each disclose a technology in which a heat dissipation layer made of a material having large thermal conductivity is so provided as to cover a thin film coil generating a magnetic flux to enhance heat dissipation, thereby suppressing occurrence of thermal protrusion.